Hardware
It has been already documented that bacterial cultures can be grown on paper in a coordinated manner with the help of inkjet printer [1]. To do this, paper is completely immersed in a toluene solution of polystyrene and then completely dried for making the hydrophobic surface [1]. Then, small patches are made by inkjet printer with toluene to form hydrophilic patches [1]. Agar is hydrolysed by sulphuric acid for appropriate viscosity and dispensed with inkjet printer [1]. Sodium hydroxide can be used to neutralise the agar and sodium sulphate can be removed by electrodialysis [1]. The agar is printed on the hydrophilic patches and can be used to grow bacteria [1]. The paper is folded in a specific manner to be accommodated inside the device as shown in the image:
Arrangement of cultured E. coli colonies after
printing on a sheet containing agar [1]
We intend to fold this paper in a convoluted manner and place it inside a packet of 0.2 micron filter paper, creating a module as shown in the image. The red section of the packet is the safe part which can be easily touched without disturbing the cultures. One can hold it to pull the module outside and expose the detection part shown in yellow. If the detection shows a color change then the rest of the module can be taken out so that the co-cultured microbes can absorb pollutants from the surrounding environment. The used module can be torn off and incinerated.
Several of these modules are packed inside a wristband in a chain, with perforated lines to tear off modules from the chain as shown in this image. The presence of air tight valve at the end of wrist band prevents the modules still inside the wrist band from geeting exposed to pollutants.
Each module is detachable and can be disposed separately. If the pollutant concentration is high, then multiple modules can be used at once. After all the modules are consumed, the wrist band can be filled again with a new set of modules. Being a wrist band, the device is user friendly. The presence of modules makes it usable multiple times.
